to troubleshoot a problem with the server, I disabled a few "virtual servers". I then enabled them again. Some of them wouldn't start to work because of mysql connection problem: mysql_connect(): Access denied for user 'penggraphics'@'localhost'
On one of the failing ones, I set the password for the database to "custom password", typing exactly the same password as the administrator one. It then worked. On two others, that procedure didn't do anything.
I've tried logging in via "mysql -u lucia -p" but it wouldn't let me connect although I'm 100% that's the mysql password.
Oops, found out how to get it working again, but think I will still post this as it might help others: change the password for the database to something new, then change it back to the old one again et voilá.
Thanks people, somehow posting here seems to do the trick already ;)